O3/Pb(OAc)4: a new and efficient system for the oxidative cleavage of allyl alcohols

Article abstract of DOI:10.1016/j.tetlet.2006.07.020

Allyl alcohols undergo oxidative cleavage, affording the corresponding carbonyl compounds in good yields, when treated with ozone-lead(IV) acetate under mild conditions.

Full text of DOI:10.1016/j.tetlet.2006.07.020

Tetrahedron Letters 47 (2006) 6619–6622
O /Pb(OAc) : a new and efficient system for the oxidative
3
4
cleavage of allyl alcohols
a
a,
a
a
a
*
E. J. Alvarez-Manzaneda, R. Chahboun, M. J. Cano, E. Cabrera Torres, E. Alvarez,
a,b
a
a
R. Alvarez-Manzaneda, A. Haidour and J. M. Ramos L o´ pez
a
Departamento de Qu ı´ mica Org a´ nica, Facultad de Ciencias, Instituto de Biotecnolog ı´ a, Universidad de Granada, 18071 Granada, Spain
b
Departamento de Qu ı´ mica Org a´ nica, Facultad de Ciencias, Universidad de Almer ı´ a, 04120 Almer ı´ a, Spain
Received 24 April 2006; revised 4 July 2006; accepted 6 July 2006
Available online 1 August 2006
Abstract—Allyl alcohols undergo oxidative cleavage, affording the corresponding carbonyl compounds in good yields, when treated
with ozone–lead(IV) acetate under mild conditions.
ꢀ
2006 Elsevier Ltd. All rights reserved.
1. Introduction
ture of natural compounds, such as sesquiterpenes 1 or
, or diterpenes manool (3), larixol (4) or cupressic acid
2
The oxidation of tertiary alcohols is a reaction seldom
utilized for synthetic purposes because of the structural
requirements of the substrate for achieving good selec-
tivities and yields. These reactions consist of one or
two-electron oxidation processes leading to rearrange-
(5).
Three reaction modes have been reported for this methyl
vinyl carbinol moiety under oxidative conditions
(Scheme 1). PCC oxidation affords transposed 3-methyl
1
2
ment, cyclization or fragmentation products.
a,b-unsaturated aldehydes I. The use of Collins reagent
results in oxidative rearrangement to a-epoxyaldehydes
II. The third reaction mode, which involves C2–C3
3
Among this type of alcohols, vinyl derivatives are of
particular interest because they form part of the struc-
fragmentation leading to methylketones III, takes place
by utilizing potassium permanganate or chromium
trioxide–acetic acid; however, in all cases the resulting
ketone III is obtained in low to moderate yields, mainly
O
O
4
,5
due to work-up difficulties. The obtention of small
amounts of the oxidative cleavage type-III methyl-
ketones has been described when some manool (3) or
AcO
OH
OH
2
1
OH
CHO
R
I
R1 R2
R : Me; R : H
OH
CHO
3
4
5
R
R
1
2
O
R
R : Me; R : OH
1
2
II
R : COOH; R : H
1
2
O
Keywords: Allyl alcohols; Oxidative cleavage; Ozonolysis; Lead(IV)
acetate.
III
*
Corresponding author. Tel./fax: +34 958 24 80 89; e-mail:
eamr@ugr.es
Scheme 1.
0040-4039/$ - see front matter ꢀ 2006 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2006.07.020

6
620
E. J. Alvarez-Manzaneda et al. / Tetrahedron Letters 47 (2006) 6619–6622
/Pb(OAc) system
Table 1. Oxidative cleavage of some allyl alcohols with the O
3
4
Entry
1
Substrate
Time (min)
Product
Procedure (%)
A (86)
HO
O
60
6
8
7
O
HO
HO
2
3
60
90
A (90)
A (82)
7
O
9
10
HO
O
4
5
60
90
A (89)
1
1
12
OH
O
A (91) B (85)
13
14
OH
O
6
7
90
60
A (94)
1
5
16
OH
O
A (91) B (87)
1
8
1
7
OH
O
8
9
60
75
A (87)
1
8
1
9
OH
O
A (81)
OAc
OAc
2
0
21
OH
a
1
0
1
75
60
—
2
3
2
HO
CHO
1
A (92) B (87)
2
4
2

E. J. Alvarez-Manzaneda et al. / Tetrahedron Letters 47 (2006) 6619–6622
6621
Table 1 (continued)
Entry
Substrate
Time (min)
Product
Procedure (%)
12
75
A (78)
COOH
OH
2
5
26
O
OH
13
75
HOOC
A (75)
2
7
28
a
A complex mixture of compounds was obtained.
O
O
O
O
O
O
R1
R2
O3
R1
R2
R1
R2
-AcO-
O
Pb(OAc)4
O
R1
R2
O
OH
OH
-
AcOH
O
OAc
Pb
OAc
OAc
Pb
O
IV
AcO
OAc
V
-Pb(OAc)2
R1
R2
O
Scheme 2.
6
larixol (4) derivatives were ozonyzed in MeOH; how-
ever, the procedure is not useful for synthetic purposes,
because a mixture of compounds in low yield is usually
obtained. The protic solvent seems to play an important
role in this ‘anomalous’ ozonyzation, because it is
known that ozonolysis of allyl alcohols, utilizing
CH Cl as solvent, affords the corresponding a-
resulting from the overoxidation of the corresponding
aldehyde. On the other hand, the primary cyclic alcohol
27 gave the ketoacid 28.
A tentative mechanism is depicted in Scheme 2. The car-
bon–carbon bond cleavage takes place via the cyclic
intermediate V derived from the hydroxyozonide IV.
This supposition is supported by the fact that the same
results were observed when lead(IV) acetate was added
after completion of ozonolysis of allylic alcohol (exper-
imental procedure B) and by the failure observed for
compound 22, which does not possess a suitable geom-
etry to form the intermediate V.
2
2
7
hydroxycarbonyl compounds in good yields. Our stud-
ies on some of compounds cited here are in agreement
with the literature data.
We have centred our attention on the latter oxidative
cleavage, which can be utilized to prepare a variety of
8
–10
synthons starting from natural terpenoids.
In order
to avoid the drawbacks involved in the use of potassium
permanganate or chromium trioxide, we investigated
alternative reagents. The ozone–lead(IV) acetate system
was found to be a suitable oxidant to achieve this pur-
pose. When an ozone–oxygen stream is bubbled through
a solution of allyl alcohol in dichloromethane contain-
ing lead(IV) acetate (1.5 equiv), the carbonyl derivative
resulting from the oxidative cleavage is obtained in good
yields (Table 1).
2
. Experimental procedure
Procedure A : A stirred mixture of alcohol (1 mmol)
and Pb(OAc)4 (1.5 equiv) in CH Cl (15 mL) was
2
2
The utilization of both procedures gave similar results (entries 5, 7
and 11 in Table 1). Oxidation of compound 20 was carried out at
À78 ꢁC, utilizing the procedure A, and monitorizing the reaction by
TLC; when the ozonyzation was carried out at 0 ꢁC, partial oxidation
of exocyclic carbon–carbon double bond was observed. In the work-
Secondary and primary allyl alcohols (entries 11–13)
also undergo oxidative cleavage. The benzylic alcohol
2
3 was transformed into benzaldehyde (24), whereas
3
up for entries 12 and 13, washing with satd NaHCO solution was
compound 25 afforded the carboxylic acid 26, probably
eluded. NaHSO was not added after oxidation of alcohol 23.
3

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E. J. Alvarez-Manzaneda et al. / Tetrahedron Letters 47 (2006) 6619–6622
slowly bubbled with an O /O mixture at 0 ꢁC for the
References and notes
3
2
specified time. The solution was flushed with argon,
and NaHSO (2 equiv) was added. The mixture was fil-
tered and the filtrate diluted with ether (25 mL), and
washed successively with sat. NaHCO3 solution
1. For a review on the metal-mediated oxidation of tertiary
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3
2
3
4
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(
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6
was dried over anhyd Na SO and evaporated to yield
2
4
the product.
8
Procedure B : A stirred solution of alcohol (1 mmol)
4
in CH Cl (15 mL) was slowly bubbled with an
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2
2
O /O mixture at À78 ꢁC, and the course of the
3
2
reaction was monitored by TLC. When the starting
material was consumed, the solution was flushed with
argon, and Pb(OAc)4 (1.5 equiv) was added. The
mixture was further stirred for 45 min at room tem-
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obtained.
7
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Acknowledgements
The authors thank Junta de Andalucia for financial
support.
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